BIOC 384Mitochondrial Electron TransportQ11.3: What explains the observation that FADH2 oxidation yields one less ATP than NADH oxidation by the Electron Transport System?

Name: BIOC 384Mitochondrial Electron TransportQ11.3: What explains the obser
Uploaded: 2024-03-20T06:42:55.000Z
Channel: Bartleby
Description: BIOC 384Mitochondrial Electron TransportQ11.3: What explains the observation that FADH2 oxidation yields one less ATP than NADH oxidation by the Electron Transport System?

Electron transport chain is a series of protein and organic molecules located in the inner membrane of mitochondria that transfers electrons from electron donor to electron acceptor through redox reactions creating electrochemical gradient across the membrane in order to synthesize ATP via oxidative phosphorylation.For each pair of electrons transferred to O2 ; Complex I, III and IV pumps 4, 4 and 2 H+ respectively to the Intermembrane space (IMS) . Complex II do not have the ability to pump protons to the IMS. Both NADH and FADH2 transfers a pair of electrons to the ETC. NADH transfers its electrons to Complex I. From Complex I, the electrons travels to Complex III and then to Complex IV and finally to O2 . So, Complex I pumps 4 H+ , Complex III pumps 4 H+ and Complex IV pumps 2 H+. So, a total of 10 H+ gets pumped to IMS as a pair of electrons from NADH reaches O2 via ETC. FADH2 transfers its electrons to Complex II. From Complex II, the electrons travels to Complex III and then to Complex IV and finally to O2 . So, Complex III pumps 4 H+ and Complex IV pumps 2 H+. Here Complex I is not involved. So, a total of 6 H+ gets pumped to IMS as a pair of electrons from FADH2 reaches O2 via ETC. An ATP synthase have an average of 12-c subunits in it. Stoichiometrically, 4 protons have to flow from IMS to mitochondrial matrix through these ATP synthases for it to synthesize 1 ATP. We know, a pair of electron transport from NADH to O2 via ETC pumps 10 H+ to IMS. So, the number of ATP molecules that can be synthesized as these 10 protons flow back from IMS to mitochondrial matrix via ATP synthase is equal to 104= 2.5 ATP molecules. We know, a pair of electron transport from FADH2 to O2 via ETC pumps 6 H+ to IMS. So, the number of ATP molecules that can be synthesized as these 6 protons flow back from IMS to mitochondrial matrix via ATP synthase is equal to 64= 1.5 ATP molecules . So, FADH2 oxidation yields 1 less ATP compared to NADH oxidation via Electron Transport System. Note : the terms Electron Transport Chain and Electron Transport System are synonymous (same) .